It will be grossly overpriced whatever it consists of. 😀😀
Well it cost me just under a fiver (£4.99) for a good quality male to male phone cord and a half hour’s fiddly work with screwdriver and wire snips. And it works. It should have been a lot faster, but my multiple extension wiring is complicated, for historical reasons. The phone line comes into our house to a connector box from which one extension is fed directly (it is very far away at the back of the property, beyond DECT range and the cable runs around the outside of the house). I’d never have got that one working without this fix.
From the incoming connector box, a cable runs to the bedroom phone socket which is wired as a master socket and feeds 2 telephone extensions both of which also have Openreach 5C Mk4 Master Sockets (They put them in, not me!) I removed the incoming wires at the first (bedroom) Master socket and plugged my router into the convenient phone socket in the hall (which is technically an extension although it’s a 5C box). No joy.
The two extensions I need to re-enable were silent. I guessed this was because they were wired from that first Master, so I reconnected the incoming pair into that little clip marked A and B and instead snipped the blue and orange wires as they come into the house at the connector box by the window in the bedroom - BINGO !
I now have two working phone extensions remote from the router and, via a two way phone splitter, I also have a hall phone plugged into the Smart Hub. Thanks to the phone gurus in this forum who spelled out how this can be done. Shame on BT for pretending that there would be no problems with my extensions, in order to get a sale. Good luck to anyone else who wants to try this and get those extensions working. I hope the detail I have given helps. You really have to remove those incoming pair of wires at their first connector.